Development of exposed sensitized mediums.



E. B@ nowmwe.

DEVELOPMENT OF EXPOSED SENSITIZED MEDIUMS.

.APPLICATION man MAR. 16. 1918.

1,302,777; 7 Patented May 6, 1919.

2 SHEETS-SHEET l- INVENTOR A TTORNEV E. B. DOWNING.

DEVELOPMENT OF EXPOSEUSENSITIZED MEDIUMS. APPLICATION FILED MAR. 16,I918- 2 SHEETS-SHEET Z- I 5.. 1-50 i 1-55 572M 2.5 E? 5:. 2.) g:- gl.2.5 2- 2- T- 2- JJIIIIIIIIIIIIIIIIIIIIIlllllllllllllllllllllIIIIIIIIIIIIIIIII A TTOR/VE Y EUGENE B. DOWNING, OI NEW YORK,-N. Y.

DEVELOPMENT OF EXPOSED SENSITIZEID MEDIUMS.

Specification of Letters Patent.

Patented May 6,1919.

Application filed March 16, 1918. Serial 110,222,817.

7 '0 all whom it may concern:

Be it known that I, EUGENE B. DowmNe, a citizen of the United States,residing in the borough of Manhattan, city of New York, county of NewYork, and State of New York, have invented new and useful Improvementsin the Development of Exposed Sensitized Mediums, of which the followingis a specification.

The invention relates particularly to the development of exposedsensitized mediums, though other features and aspects of themventionwill be alluded to hereinafter. In developing such mediums, that is tosay positive and negative films, positive and negative plates, etc., itis necessary that certain factors be known and strictly observed ifperfect results in developing are to be secured. Some of the factors maybe known,

but the most important of them must be determined, and within thislatter group falls the unknown value or actual Working energy of variousdevelopers. Their energycannot be determined merely by knowledge oftheir composition; neither can they be determined by the most expert byobservation of the sensitized medium in its process of development whenilluminated only by the subdued and uncertain dark room light.

In developing these mediums there is but one point of development towhich they should be carried to produce the proper gradation of shadeand intensity which constitutes perfect development. Any greater orlesser degree of development produces imperfect results.

To determine correct development visually by dark room light is aphysical imposslbility. This is especially true of motion picture ,filmson account of the small size of the image. Consequently the resultssecured by the most expert dark room man are only approximately correctat best and usually the results of his efforts are no better than toperfect. Thus, in the case of a ,film upon which thousands of dollarshave been carefully spent to produce a work of art and beauty, from 15to 50% of the perfection already attained is usually lost in the darkroom by imperfect development. Furthermore. the exaggerated contrasts indensities and lack of proper gradations and softness of tone causestrains to the eyes and nerves of thousands and millions of persons whomay view the work upon the screen.

'It is, therefore, of the greatest lmportance that some method and meanshe provided for accurately ascertaining the working energy of developingsolutions and the actual time required to produce 100% perfectlydeveloped films and plates.

A developer may be known to be of a certain strength and of any of theknown standard developing agents, but its actual Work ng energy at anyparticular time will remamunknown, as many things influence the actlvltyof developers, such as changes of .temperature, use, a e, alkali,"etc.,so that perfectly developed film in eight minutes and forty seconds at atemperature of'60 F. With the same solution without any other changethana rise of temperature to 68-} F. perfect development was secured inexactly four minutes and five seconds. Thus the working energy of thedeveloper was, increased more than 100% by a rise of 8119 intemperature. l

The time of exposure given to a sensitized medium does not control orinfluence the time of perfect development of said medium in the least,but imperfect exposures, that is to say under and over exposures, dodeceive the dark-room man in his visual process of development whereapparent intensity is his only guide. He will invariably judge an overexposed plate or film to be fully developed beforethc relatively correctsteepness of intensity and gradations has been attained. Consequentlyflatness and lack of life is the result. In the case of under-exposurehis guide is again false, and for lack of normal visual density, heforces development and discounts perfection, in many cases to a totalloss.

The time of correct and perfect development of a normally exposed plateor" film under certain conditions is also the only, time of perfectdevelopment for all classes of exposure, under exposed and over exposedincluded.

Under-development produces flatness, dullness and relatively. imperfectand low gradations of intensities and half-tones and lacking in itsrelatively corresponding high lights. Uver-development, however slightit may be, produces harshness, exaggerated contrasts and a distortedscale of gradations, also serious loss of detail, unsightly dark shadowsand highlights take the place of the once attained soft and harmonioustones.

Perfect development produces a harmonious scale of perfectly graduatedintensities, highlights, half tones and shadows, which will in the mostartistic and perfect way represent the'subject photographed.

The secret of perfect developing is to know the speed or work ing energyof the given developer. Allow 100% to mark the point of perfection indevelopment. The Working energy of the developer having been-ascertainedto a degree of certainty, then bya simple calculation, we knowdevelopment of our negative, for example,

must continue to the last expired moment of a well defined period oftime in order 'to attain that supremehigh degree of perfection, andimmediately or instantly thereupon development must cease if thatperfection is retained. If not, perfection is rapidly discounted. 100%perfect development'has no latitude; like a stone cast into the air,when it reaches its top most height, that point also marks the beginningof its down-fall.

It is a well known fact among earnest- 'students of photography thatwith any developer when developing properly exposed plates' or films ofany subject which contains the ordinary scale of bright lights and Idark shadows or bright and dull colors or both, the time of the firstvisible appearance of the image bears a fixed relation or is a constantfraction of the time required to se cure absolutely perfect development.

The factor or co-efiicient of all known developers yary from 4 to 34. Myextensive experiments ave proven to me that in order to ascertain thetime of perfect deevlopment of exposed sensitized mediums in any givendeveloper, the time of first visible appearance must be ascertained to amarked degree of precision-and certainty. That is, it should beregistered in seconds and not in greater time units, which would onlyapproximate the time of first appearance. For instance, my experimentshave often proven, that 17 seconds for example, the first appearance wasdistinctly visible, in 18 seconds it was more distinctly visible whilein 16 seconds it was not visible at all. Consequently, it is obviousthat for precision in perfect development, the time of thefirstapp'earance should be recorded in the shortest unit of time which willmark a difference.

Consequently a co-efiicient of activity may perceptible be determinedfor any developer by ascertaining the exact time required for correctdevelopment under a given set of conditions, then findingbtlie exacttime to produce the faintest vis' le image or appearance in the samedeveloper and under the same conditions, and taking the ratio of thesevalues; in other words, dividing the time of complete and perfectdevelopment by the time of the first visible appearance. Thiscoefficientwill hold good for the given developer or any developer made of exactlythe same constituents and proportions at all times and under allconditions. Thus, if the time of perfect development he five minutes andthe time of the first visible appearance be one minute, the coefficientof activity of the developer is 5. The actual activity or energy of thedeveloper may be increased 100% by arise in temperature alone. The firstvisible appearance would then occur in thirty seconds. If this value bemultiplied by the coeflicient 5, the result would be two and one=halfminutes, which would be the correct time for perfect development underthe changed condition. If by constant use or a lowered temperature theener of the same developer was reduced until the first appearance becamevisible in three minutes, then multiplying this quantity againby thecoefficient a result of fifteen minutes is obtained, which is theabsolutely correct time for perfect development in that solution underthose conditions. Consequently having once ascertained the coefiicientof a developing solution, I propose at any time thereafter when films orplates are to be developed to determine the time of perfect developmentunder the then existing conditions by ascertaining the time of firstappearance of image at that time and multiplying this by the previouslyas- I minutes short of or exceeding the time of correct and perfectdevelopment in such case; With a co-efiicient of 5, an error of fiveseconds in the time of first appearance would result in an error oftwenty-five seconds in the calculated time of correct and perfectdevelopment. In either case the imperfection in the result caused by theerror would be serious.

'lVhile this process appliesto all sensitized developing mediums such aspositive and negative plates and films, 'bromid papers, etc., 1n orderto avold confusion and more elaborate and extensive explanation of theprocess and its requirements in the way of apparatus, I will refer moreespecially to the I development of motion picture films.

In the accompanying drawings:

Figure 1 is a semi-diagrammatic side sectional view of'an apparatus forcarrying out the invention;

Fig. 2 is a side elevation on a smaller scale of an alternativeapparatus;

Fig. 3 is a planview of Fig. 2;

Fig. 1 is a face view of a chart from which an indicator may be producedphotographically;

Fig. 5 is a face view of such indicator after being progressivelydeveloped, the same being shown in its holding frame; and

Fig. 6 is a face view of another chart.

In order to. ascertain the time of first visible appearance of the imagewith certainty and despatch, I provide myself with a strip of motionpicture film or other suitable sensitized medium on which ll secure alatent image of one of my charts to be used as the indicator. This canbe done by a direct process of photography, that is, place thesensitized medium in the camera andsecure the latent image by directlyphotographing the chart. Or it can be secured by printing from apreviously made negative of the'chart. However, in either case, theexposure should be correctly made. I now subject successive portions ofthis exposed medium to the action of the developer, for successivelygreater or less predetermined periods of time. The successive .periodsof time, predetermined to correspond relatively to the successiveportions, divisions, or gradations of my indicator. When the lastportion or division of my indicator has been subjected to the action ofthe developer, for the period of one second, the action of the developeris then immediately arrested by dashing the indicator or exposedsensitized medium in a solution of water acidified with sulfurous acid.Thereafter, this indicator can be examined by any source of white light,without suffering any perceptible change. lit will be observed by theaccompanying drawings herein given for the purpose of illustration thatI provide means to support my sensitized indicator, in

the developing cylinder of the apparatus in such a way that the top ofsection No. 1

title of my indicator comes flush with the top of the developingcylinder or receptacle; consequently, when the developer rises to thepoint ofoverfiow, this indicates without the use of a watch, the exacttime, to remove the indicator and arrest the development. We will assumefor example that my indicator is fifteen inches long and divided into120 equal parts, or in equal divisions of inch each. Each part orsection preferably numbered, commencing with No. 1 at the top and eachof the successive lower sections, successively numbered 2, 3, 4, etc.,

while the top section or No. 1 will have received one seconddevelopment.

While the image will be very clear and distinct and possibly even darkat the bottom section of this indicator, the top section or No. 1 andother sections near the top, will remain blank for the want ofsufiicient development to create a visible image. But continuing fartherdown from the top, the first visible image will be a number, which willI be faint but clearly readable and this number will represent inseconds, the exact time of developmeint required to produce that faintvisible image. Proceeding from this point downward, each successivesection of my indicator, by reason of'having received successivelygreater periods of development will be successively stronger andstronger all the way to the lower end, or the last section No. 120; andfrom the faintest image downward, each separate section automaticallyandin legible figures, representing seconds of time, gives the exacttime period .of development it has received. Consequently, by visualinspection to be'made by good i and suflicient light, either with orwithout a simple calculator, according to the design of the indicator,the time offirst appearance 100. can be arrived at immediately and withabsolute certainty.

There are variousways in which such a strip or indicator may beprogressively developed. I prefer, however, to place it u pright in asuitable fram within an upright receptacle and to admit the developerto, the receptacle at a predetermined rate, so that the developer risesup the strip. Thus, if the rate of supply be fixed so that the developerrises one division upon the indicator per second and if the progressivesubmersion be continued until the developer covers the top division, theindicator being then at once removed and placed im'an acidulated bath tostop the development, it will follow that the said top division hearingthe numeral 1' will have been in the developer one second, the nextlower division marked 2 will have been in the developer two seconds, andsoon down to the bottom. Consequently the time of first appearance maybe ascertained by direct reading of the division or section or portionofthe indicator where the image, numeral or we otherwise, first appears.Thus, if thenumber of this section is 1'5 and'the coeficient of thedeveloper be 5, it is at once found that the time of perfect developmentunder the then existing set of conditions will be we gressive submersionby lowering the indica-' tor at a predetermined rate into a standingbody of the developer. It will be understood that the relative movementbetween the indicator and the developing fluid may be I eithercontinuous or intermittent.

In making the indicator I first produce a chart A, by drawing orotherwise, such as shown in Fig. 4. For purposes of illustration thischart is shown as a strip bearing graduations and numerals from 1 to 40in solid black upon a white ground. How-.

ever, white upon a solid black ground is equally effective. Of course itwill be understood that this chart may be of any size to best suit myrequirements and to extend to sections or numbers greater than 40 andalso be'it understood that the chart may be a scale only and withoutnumbers, which in such case can later be compared with a scale ofnumbers, having relatively or correspondingly the same scale ofdivision; or, the chartanay be of numbers only, having predetermined orknown degrees of separation.

' The successive markings may be made like or similar to an ordinaryruler or yard stick, or as the measured markings of a thermometer, orany other markings or scale of-measure divisions, lines, figures,letters, symbols, characters or designs which will provide the means ofcalculation for ascertaining to a degree of constant precision, the timerequired to secure the-first visible appearance of image or indicate thetime of perfect development.

For illustration, referring again to Fig. 4, by photography I obtained aperfect negative. of this chart, enlarged or reduced or of a the samesize, depending upon the size of scale desired for my indicator. Fromthisnegative by iproper exposure upon our motion picture lm or othersuitable sensitized medium, I secure a latent image of my chart; one ofthese prints constitutes the letter B, for convenience is retained in asuitable frame "C, which holds it rigid. Now by progressively developingthe indicator until, as in this illustration, section or division No. 40hashad its 40 seconds development, and each successive number ordivisionabove has had successively one second less develo ment,

at until this top section or No. 1 is reac ed by the developer andreceives as its number indicates, one,second of development, thereuponinstantly arresting the development, the result may be secured such asFig. 5. Here all the upper part of the indicator from No. 1 to No. 26,inclusive, is completely under developed and blank. At the 27thdivision, is a faint or so called first visible appearance and withinthis section number "twenty-seven appears as the image, faint but easilyreadable. From this division down, the images become successively darkerand more intense. Therefore it is obvious that in the case of sectionNo. 26, this number did not appear on the indicator for the lack of onesecond more development. Consequently in this particular instance, thisparticular developer and under the particular conditions obtaining,ithe'time of first appearance ofthe image twenty-seven, was 27 may bedesigned.

Fig. 1 illustrates in a schematic manner a form of apparatus foreffecting progressive development of the indicator. The said apparatuscomprises an inverted bottle 2, containing developer, and representingthe source of supply, said bottle being re )resent ed as supported uponan arm 3 ad ustable upon a standard 4 rising from a suitable base 5.Beneath the source upon the base 5 is a feed reservoir 6 open to theatmosphere and provided with means for maintaining a constant level orhead therein. Such means may comprise an outflow tube 7 and an air inlettube 8 passing through the plug 9 in the mouth of the inverted bottle,the tube 7 projecting downward below the lower end of the tube 8. Aswill be readily understood this organization will not permit the waterin the reservoir 6 to rise higher than the lower end of the air tube 8,while descent of the level below this point will permit en trance of airto the bottle and cause liquid therefrom to flow into the reservoir andthus bring the level back to the fixed point. The upright receptacle 10,in which the indicator in its frame C is placed, is seen suitablysupported below the reservoir 6.- It remains now to provide thereservoir 6 with an outlet which will cause the developer to'enter thereceptacle at the desired predetermined rate, that is to say at suchrate that the developer sufficient length will contain both thedivisions of the indicator. It will be understood that-for indicators ofdifferent heights, receptacles of different heights may also beprovided. The pipe 11 also bears a shut-off cock 13, and in order toprevent splashing in the receptacle 10, the conduit may be continued tothe bottom by means of tubing 14.

Figs. 2 and 3 represent a form of apparatus wherein a receptacle 10contains a standing body of developer, while the indicator frame C israised or lowered into or out of the body at a predetermined rate bymeans of clock work 15. For purposes of illustration the frameC isshownformed upon'one edge with rack teeth 16, which are meshed by apinion 17 of-the said clockwork, while the opposite edge of the frame isguided in a grooved guide 18. In order to permit the frame and indicatorto be instantly removed or inserted, the said guide is shown as hingedat 19 to a suitable support 20 and held by a spring 21 to its operativeposition. A handle 22 on the hinged guide enables it to be thrownquickly open, so that the frame can be raised .or lowered clear of thepinion 17 Reference may be made to the matter of toning. The toning offilms adds a certain degree of intensity. Consequently when films are tobe toned, it is desirable to stop the development correspondingly shortof the time of perfect development. The amount of the intensity addedby'toning can be ascertained and due allowance made in the indicatorsand in the procedures heretofore described.

I have not heretofore described the method of arriving at thecoeflicient of activity of any given developer in the first nstance.This is done only once and it is not particularly important whether themeans and method employed are expeditious or not.

However, it will be apparent that the inven-- tion provides a way ofascertaining the coefiicient very easily. All that 1s necessary is toplace a strip of properly exposed motion I picture film, for example, inthe apparatus of Fig. 1, again by way of example, and to set the valve12 so as to admit the developer at the appropriate rate. This strip be1nof rst visible appearance of the image and also sec- ;"lions which aremore than correctly developed. Between the lower end of this stripcompared with perfect results.

, ing

and the faintest visible image above, will be found a section which hashad correct and absolutely perfect development, and on either side ofthis will be found several other sections that approximate correctdevelopment.

However, near the approximation their imperfections will be clearlynoticeable when Knowing the rate of rise of the developer, it is veryeasy to measure with a ruler ora specially devised measure, andascertain both the time of first visible appearance and the time ofperfect development, and thus the unknown factors or coeflicients areattained. Still another use of the apparatus of the invention in itsvarious forms may be alluded to. This is the tinting or colorin offilms. By ordinary methods it is diflicu t to secure or to reproducejust the exact shade of any color which may be desired for a particularfilm. In order to secure any desired tint or color in photographs,films, plates or paper, positives or negatives, I propose to provide ascale of perfectly graduated shades of each color, ranging from thefaintest per: cepti ble shade to the deepest color practically used.Such a scale can be made on films or plates and will serve as a standardscale or chart for future comparison. These scales can readily beproduced by progressively submerging a strip of film itself, or thelike, in the desired dye in any of the forms of the apparatus of theinvention. Such color chart may be graduated and may bear numbers, orthe time of immersion necessary for any shade at any point along thescale may be ascertained by placing the scale alongside a rule,graduated to come spond to the rate of submersion of the strip in thedye.

What I claim as new'is:

1. Method of determining the time of perfect development in a givenphotographic developer under a particular set ofconditions, whichcomprises initially ascertaining the time of perfect development and thetime of first appearance of image with the developer under the existingconditions, takthe ratio of these values to obtain the coefficient ofactivity of the developer, thereafter when exposures are to be developedsubjecting successive portions of a sensitized exposed indicator havinsmall equal subdivisions to the action of t e developer for knowngraduated periods of time, arresting the development, and from the timeof first appearance of image on the indicator multiplied by thecoeflicient of activity ascertaining the time of perfect developmentfect development in a given photographic developer under a particularset of conditions, whlch comprises subjectlng successive portions of asensitized exposed indicator havlng small equal subdivisions to theaction of the developer for known graduated periods of time,arrestingthe development, and

multiplying the thus ascertained time of first appearance of the imageby the coeflicient of activity of the developer.

3. Method of determining the time of per fect development in a givenphotographic.

developer under a particular set of conditions, which comprisessubjecting successive portions of a sensitized exposed indicator havingsmall equal subdivisions to the action of the developer for knowngraduated periods of time, arresting the development, and from the timeof first appearance of image multiplied by the coefiicient of activityof the developer ascertaining the desired time of perfect development.

4. In a method of determining the time of perfect development in a givenphotographic developer under a particular set of conditions, the stepswhich comprise subjecting successive portions of a sensitized exposedindicator to the action of the developer for acey??- known raduatedperiods of time, and immediate y arresting the development, in order toascertain the time of first appearance of image.

5. In a photographic process, the steps which comprise immersing asensitized exposed strip having small equal subdivisions in a developerat a predetermined rate, and

